1. Department of Fish, Wildlife, and Conservation Biology and Graduate Degree Program in Ecology; Colorado State University; Fort Collins CO 80523 USA
2. U.S. Geological Survey, Forest and Range Ecosystem Science Center; 3200 SW Jefferson Way Corvallis OR 9733 USA
3. Trophic Cascades Program; Department of Forest Ecosystems and Society; Oregon State University; Corvallis OR 97331 USA